In recent years, there has been increasing needs for electronic devices each having an impact resistance and flexibility, and electronic devices in which electronic circuits including electronic elements are formed on a surface of a resin film which is frequently used. An example of such devices is applied to a variety of electronic devices including displays such as liquid crystal displays or organic EL display devices, solar batteries and touch panels. In the case of manufacturing these devices, electronic elements or the like need to be formed on a flexible substrate, however, if an attempt is made to directly form an electronic element on the flexible substrate, since a part of the resin film is floated or curbed, thereby the flatness of the resin film is degraded, the electronic elements or the like cannot be formed in an accurate location. Thus, the electronic elements or the like are formed in a state in which the resin film is brought into intimate contact with a surface of a supporting substrate, and thereafter the resin film is released from the supporting substrate. In this case, on the resin film, the electronic elements and circuits are formed and thus it is needed to be released without imparting a stress to these elements or the like. Therefore, there is conventionally used a method for irradiation with laser light beams or light with a short wavelength by a flash lamp (hereinafter, referred to as laser light beams or the like), thereby weaken an intimacy force (adhesion) between the resin film and the supporting substrate, and then the resin film is released.
However, if irradiation with laser light beams or the like is carried out, in some kind of the electronic elements formed on the resin film, a special characteristic of the electronic elements themselves may degraded by laser irradiation with laser light beams or the like. Also, in order to release the resin film by irradiation with laser light beams or the like, a large, and expensive irradiation apparatus is required. Accordingly, in an example disclosed in Patent Document 1 for instance, as shown in FIG. 7, an adhesive layer 92 is formed at only a peripheral edge on a supporting substrate 91: on the adhesive layer 92 and all over the inside of the adhesive layer 92, a resin film 93 is formed; and on the resin film 93, an electric element 94 is formed and thereafter only a part of the adhesive layer 92 of the peripheral edge is irradiated with laser light beams or the like, and the resin film 93 and the supporting substrate 91 are separated and the supporting substrate is removed. That is, the resin film is bonded only at the peripheral edge of the supporting substrate 91, and is hardly bonded at the central part thereof, and further a part of the adhesive layer 92 is irradiated with laser light beams or the like to thereby weaken an adhesive force. However, in this method, even a small range of the peripheral edge must be irradiated with laser light beams or the like, and therefore, there is a need to prepare an expensive irradiation apparatus.
In addition, in Patent Document 2, as shown in FIG. 8A, a release layer 95 is provided at a central part of a supporting substrate 91, and on the release layer 95 and the supporting substrate 91 around there, a resin film 93 is directly formed. At this junction, the resin film is joined so that the adhesion between the release layer 95 and the supporting substrate 91 is greater than the adhesion between the release layer 95 and the resin film 93. Afterwards, in the location indicated by the arrow C in FIG. 8A, that is, at a part of the resin film 93 on the release layer 95, the resin film 93 is cut, thereby as shown in FIG. 8B, the resin film 93 on the release layer 95 with a weak adhesion is separated and then the resin film 93 is released.